Acoustic device



R. BLAIR ACOUSTIC DEVICE Dec. 24, 1935.

Filed March 2, 1951 2 Sheets-Sheet l 0 0 0 0 \m 0 0 0 0 0 0 0 0 0 0 0 0 O O O Q 0 O O 0 0 0 0M0M0 0 0 0 0 0 0 0 0 000 00000000000 0000000000 0000000000 v w0w0w0w0w0w0w0n0w0w0n u wowowovvvvvv Dec. 24, 1935. I R BLAIR I 2,025,087

ACOUSTIC DEVICE Filed March 2, 1931 2 Sheets-Sheet 2 Patented Dec. 24, 1935 UNITED --STATES ACOUSTIC DEVICE Application March 2, 1931, Serial No. 519,326

Claims.

This invention relates to an acoustic device and method of manufacturing the same and more particularly to the type having a movable speech coil mounted upon and moving with a sound reproducing frusto-conical diaphragm of suitable material. It has been a common practice in the manufacture of electrodynamic speakers to carry the flexible lead along the surface of the diaphragm to a point sufficiently far removed from the speech coiland its support so that its movement at this point is relatively small.

An object of this invention is to connect the terminals of the speech coils to the external circuit without making use of the diaphragm. This has been accomplished by connecting the external circuit to the movable coil by flexible leads attached and carried by a portion of the coil support that moves through the same amplitude and at the same frequency as the movement of the speech coil per se.

Another object of this invention is to provide a spider with ears mounted intermediate the diaphragm and the speech coil support, said ears functioning as rigid supports for the junction intermediate the flexible leads and the fine coil w1re.

Another object of this invention is to provide a movement for the diaphragm that may be completely assembled as a unit before attaching the diaphragm.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred embodiment of one form of the present invention is clearly shown.

In the drawings:

Fig. 1 discloses a sectional view of an electrodynamic acoustic device.

Fig. 2 represents a fragmentary sectional view taken substantially on the line 2-2 of Fig. 1.

Figs. 3, 4,'and 5 disclose an enlarged fragmentary sectional view showing successive steps of assembly.

In the drawings the reference character It indicates a support for a cone diaphragm i2, provided with a flexible edge I 4 made from leather or impregnated cloth or any other suitable flexible material and clamped intermediate the flange l6 integral with the support I0 and the clamping ring I8 by a series of screws or any other suitable fastening means. The support It carries a magnetic housing 2| provided with a center pole piece 22 either riveted or Welded together.

f In order to reduce the flux density in the bottom portion 24 of the magnetic housing 2! a steel Washer 26 has been used in reenforcing' the bottom 26 thereby reducing the flux density in the bottom. An annular pole piece 28 is spot welded or otherwise attached to the magnetic housing 26 and so positioned as to form an annular air gap 30 with the center pole piece 22. In order to prevent the field windings Sd from coming in contact with the speech coil 36 a packing washer 38 has been placed between the annular field pole piece 1 28 and the winding 34. The terminals ii] and 42 of the field winding 33 are positioned in a suitable slot 44 in the packing washer '38 and a slot or aperture 46 in the annular pole piece 28.

A flexible spider 50 held in position by screw 5| 15 centers the small end of the frustro-conical diaphragm l 2 with respect to the center pole piece 22 and exerts a restoring force upon the diaphragm l2 during and after each displacement of the diaphragm. The restoring force of the spider 50 is augmented by the restoring force exerted by the flexible edge is which is loosely interposed between the large end of the frustro-conical diaphragm l2 and the support I 0. Normally there are no internal stresses in the diaphragm I2 as it is neither in tension nor in compression. As best seen in Figs. 3 and 4 a driving movement of the diaphragm 12 includes the coil 36, the coil support 31, 38, the spider 50, and the spacing members 52 and 54. A frustro-conical member 56 is attached by cement or any other suitable means to the flange 58 integral with the coil support 3'! so as to reinforce the flange 58 whereby the flange moves as a unit. The spacing member 52 is placed intermediate the flange 58 and a coil 36 so as to prevent the coil 36 from creeping on the coil support and so as to reenforce the coil support 37 intermediate the point of application of force and the point of delivery of force. This spacing member 52 is provided with a gap 66 through which the ends of the speech coils 62 and 64 pass. After the coil 36 has been wound on a suitable form, not shown, and after the terminals 62 and 6d have been placed in the position disclosed in Fig. 3, a suitable wrapping material 65 is wound over the spacing member 52 and intermediate the outer winding of the coil 36 and the flange portion 58 so as to reenforce the coil support between the coil and the flange 58 and so as to hold the leads 62 and 64 in a fixed position. After this is done the leads 62 and 64 are passed through the eyelets 66 and 68 that have previously been inserted in the tabs 10 and i2 respectively, integral with the spider 50. The r eyelets 66 and 66 attach the ends of the flexible prising a frustro-conical diaphragm, and a moveleads l4 and 16, provided with metallic clips 18 and 80 to the tabs 10 and 12. In order to insure good electrical connection between the terminals 62 and and the flexible leads (4 and 16 the ends 62 and 64 are preferably attached to the metallic clips 18 and 80 by solder as indicated at 82 and 84.

The method of assembling the movement and the diaphragm includes the following steps: As the support 31 has been formed and the spacing member 52 attached thereto the coil 36 is wound on the coil support 31 while it is mounted upon a suitable support, not disclosed. When the coil 36 has been wound the terminals 62 and 64 are left in the position disclosed in Fig. 3 and the reenforcing strip is preferably made of tissue paper and wrapped intermediate the coil 36 and the flange 58. The spider 56 after being punched from sheet or fibrous material is provided with a frustro-conical edge as disclosed in Fig. 4 by being placed in a die, not shown. The pig tails 14 and 16 are now attached by means of the eyelets ,66 and 68 to the tabs Ill and 12, respectively.

The spider assembly 50 is then attached to the flange 58 by cement or any other suitable adhesive so as to complete the entire movement. The terminals 62 and 64 are then put in place and attached to the metallic clips 18 and 80 by solder. The movement is now ready to be attached to the diaphragm l2. It will be noted that all of the parts on the movement are rigid with respect to each other with the exception of the pig tails l4 and 16 per se, so that the terminals 62 and 65 move through an amplitude that is alwaysequal to the amplitude through which the movable speech coil 36 moves so that there is absolutely no flexing in any of this portion and no flexing within the movement per se. Of course, the center of the spider being attached to the center pole piece 22 flexes to permit the diaphragm to vibrate. The diaphragm is now attached to the movement by cement or any other attaching means.

While the form of embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows: 7 1. In an acoustic device, a vibrating unit comment, said movement including, a coil, a form for 'said coil, said form being provided with an integral flange, means for securing said form to said diaphragm comprising an annulus provided with tabs, said annulus being attached to said flange and disposed intermediate said coil form and said diaphragm, and flexible connections 5 from said coil to an external circuit, said connections being attached to the terminals of said coil on said tabs, whereby the coil and its terminals move as a unit.

2. In an acoustic device, a vibrating unit comprising a frustro-conical diaphragm, a magnetic frame, and a movement, said movement including a coil frame, a speech coil thereon, and a centering spider secured to the speech coil and to the magnetic frame, said centering spider having protruding ears, means carried by the ears independent of the part thereof secured tothe magnetic frame, for supporting the juncture of the speech coil terminals, and leads from the external circuit so that the speech coil and its terminals move as a unit.

3. A movement for an acoustic device comprising a movable speech coil, a cylindrical support for said speech coil, said support having a frustroconical flange, a centering spider, having a 2:3 frustro-conical flange, said first flange being secured to said second flange, said second flange having a protruding ear for supporting the juncture of the speech coil terminals and flexible terminals of an external circuit so that the speech coil, its support and said juncture move in unison.

4. A movement for an acoustic device comprising a movable coil, a cylindrical support for said coil, said cylindrical support'terminating in an annular flange portion, a centering spider having 1 3 a an annular flange portion attached to said first flange portion, said spider being provided with ears, gromets in said ears for attaching the terminals of the movable speech coil to the external circuit, so that the coil, its support and said ears move in unison as a single unit.

5. A movement for an acoustic device, comprising a movable coil, a, cylindrical support terminating in an annular flange portion, a coil spacing member intermediate the flange and said coil, t5 the terminals of said coil extending parallel to the axis of the coil said terminals passing through a gap in said spacing member, a spider for center- 7 ing the speech coil attached to said coil support, said spider having ears for carrying the juncture of the speech coil terminals and the terminals of an external circuit.

ROBERT BLAIR. 

